Scanning electron microscopic evaluation of the internal fit accuracy of 3D-printed biphasic calcium phosphate block: An ex vivo pilot study

The aim of this study was to assess the internal fit accuracy of a three-dimensional (3D)- printed biphasic calcium phosphate (BCP) block compared with a 3D-milled poly methyl methacrylate (PMMA) block by scanning electron microscope (SEM) analysis. In a total of 20 porcine rib bones, two different types of defects having two adjacent walls and a floor were produced: a defect with a flat floor (flat defect; N = 10) and a defect with a concave floor (curved defect; N = 10). Each defect was grafted with either the 3D-printed BCP block or the 3D-milled PMMA block fabricated following the computer aided design. The defects were then cut cross-sectionally and evaluated under the SEM. The extents of internal contact and gap were measured and statistically analyzed (p < 0.05). All blocks in both BCP and PMMA groups were successfully fit to the flat and curved defects. The internal contact ratio was significantly higher in the BCP group (flat defect: 0.47 ± 0.10; curved defect: 0.29 ± 0.05) compared with the PMMA group (flat defect: 0.21 ± 0.13; curved defect: 0.17 ± 0.04; p < 0.05). The internal gap area was similar between the two groups regardless of the defect types (p> 0.05). The internal fit accuracy of the 3D-printed BCP block was reliable in both the flat and curved defects when compared with the accuracy of the 3D-milled PMMA block.